Adjustable bracket structure



Jan. 5, 1954 A. c. PERBAL ADJUSTABLE BRACKET STRUCTURE 2 Sheets-Sheet 1 Filed June 26, 1950 INVENTOR. ALBERT C. PERBAL bz waat/ Patented Jan. 5, 1954 UNITED STATES PATENT OFFICE ADJUSTABLE BRACKET STRUCTURE Albert G. Perbal, Lake Arrowhead, Calif.

Application June 26, 1950, Serial No. 170,389

7 Claims. (01. 248-280) Thi invention relates to improvements in adjustable, freely movable supporting structures of the kind described in my United States Letters Patent Nos. 2,200,518 and 2,299,251. Such has a jointed arm extending from a base part, pivoted thereto so that its sections are movable in vertical planes. The weight of the arms and the supported object on the outer end thereof is counterbalanced by the force produced by a spring located in or on the base part. The spring force is transmitted to the several arm sections in such manner that the entire bracket is in static equilibrium in all positions thereof.

In the device of the present invention the gravitational forces acting on the outer arm section, and those acting on the bracket as a whole are transmitted to a rotatable shaft carried by the inner arm section. These forces tend, respectively, to turn said shaft about its own axis and to displace it bodily. They are opposed by a force produced by a single spring, connected to the shaft in a manner to impart rotational and translational forces'which are substantially equal and opposite to those produced by the said gravitational forces, whereby to effect an equilibration of the entire ystem.

An object of the present invention resides in the provision of an improved spring counterbalancing mechanism for a bracket structure of the character described. Since the bracket arm is adjustable and permits the supported object to be located at various distances away from the base, or primary point of support, the moment of the load force acting on the bracket will vary in direct proportion to the horizontal distance intervening the object and the point of support. The present invention affords an improved spring created counterbalancing force of substantially constant value, and improved means for applying said force to the several portions of the bracket arm, whereby to equilibrate them in all of many positions in which they may be arranged.

Another object is to provide an improved mechanism of this character which lends itself advantageously to being wholly enclosed within the base and arm members of the device.

Other objects are directed to constructional provisions that effect economies in manufacture.

Other objects and advantages will appear from the following description and accompanying drawing wherein:

Fig. 1 is a side elevational view of an adjustable lamp support constructed in accordance with the teachings of the present invention;

Fig. 2 is a fragmentary view of the inner bracket arm assembly, shown partly in section;

Fig. 3 is a sectional view through the hinge joint connecting the inner and outer arms, as taken at line 33 of Fig. 2;

Fig. 4, a sectional view, illustrates clamping means for anchoring the belt cord to the outer arm pulley, the section being taken at lined-4 of Fig. 2;

Fig. 5 is a transverse sectional view taken at line 5--5 of Fig. 2; a

Fig. 6 is a vertical sectional view through the base assembly taken at line 6-6 of Fig. 5;

Fig. 7 is a vertical sectional view taken through the base assembly at line 'l'! of Fig. 6;

Fig. 8 is a transverse sectional view through the base assembly taken at 8-8 of Fig. '7, and

Fig. 9 is a detail section taken at line 9-9 of Fig. 7.

Referring now by numerals of reference to the drawings, in Fig. 1 there is illustrated a bracket structure which is generally representative of the present invention, shown therein to consist of a base iii, an innerbracket arm section I I, an outer arm section l2, and the load object It in the form of a lamp head, pivotally mounted at the extremity of the outer arm.

The base l0 comprises a vertically elongated housing having an internal frame l4 that pro.- vides a support for a spring mechanism, to be subsequently described. An enclosure shell section i5 is rigidly and permanently secured to the frame [4 and combines therewith in the formation of an annular bearing race It that surrounds an opening in an upper side wall portion of the base. A detachable shell section or cover ll completes the base housing structure.

The inner and outer arm members H and I2 are hollow. Each preferablyconsists of a pair of complementary sheet metal stampings which are joined together along their longitudinal edges. The inner arm stamping Ila has a laterally projecting hub at its inner end, said hub consisting of a fiat disc l8 Welded or otherwise fastened to the outer face of stamping I la, and a cupped disc l9 similarly secured to the outer face of disc 50. The discs 18 and I9 coact to provide an annular bearing race at the periphery of the hub. A best appears in Fig. 6 this hub assembly extends laterally into, and is journalled in the base 10 by ball bearings 20 which are confined within and between the said annular race portions of the base and hub.

The outer arm I2 is made up of paired stampings [2a. and H21), joined together along their longitudinal edges. This arm is provided at its in her end with a laterally projecting hub 2! (Fig. 3) fixed to the said arm by bolts 22 and formed to provide a peripheral groove to receive and hold antifriction bearing 23. Such bearings are disposed in a bearing race in a lateral boss 24 formed on the outer end portion of the inner arm, and specifically on the arm stamping Ila. This arm hub 2| has a pulley 25 fixed thereto, which pulley is di sposed within the inner arm. I I. axial open; g "26 ftha tjextends through thefsaid hub andpulley'providesa passageway'for a flexible electric conductor 21, leading from the interior of inner arm H to the interior of outer arih 12. A passageway for the said conductor, from the base housing to the inner arm is indicated at 26a.

The lamp head [3 is shown to havea suitable pivot means 30 by which it is mountedon the outer end of arm l2 and is supplied withelectrical current by conductors 21.

, vFrom the description'thus'far it 'willbennderstood that the outer'armsection I2 is mounted on the inner arm 1H so'as topivotthereon in'a vertical plane, and the inner arm "is similarly mounted on the base's'tructure H). The said base structure is; preferably rotativelysupported at its lower endbya'standard orother typ'e'of mount, indicated generally by the numeral '3 I, to

permit the entire bracket to "be turned about a vertical axis on the said mount. QThe, nounterbalancing means for the several arm sections'ofthe'bracket incl'udea shaft 32 rotatably mounted'on the-inner arm H'and extendingeccezitrioally through the hub "portion ll-l9 thereof. The axis of the shaft '32is parallel to and spaced a short distance from "the "pivotal axis of theinner'arm (indicated by the letter a) in the direction directly opposite'that \in'which thearm extends. Accordingly,"the inher ,arm II is a lever fulerumedatthe' axis a, and; having a relatively long; leverarm portion extending inone direction a'nd "a' 'relativelyshort leyenarm; portion terminating at the axis of shalt", extending in the opposite direction from One end of shaft 32 projectsinto the "interior piiltheiarm .l1 and such (and has fixed'thereon a pulley 33 ofthexsametdiameteras'pulley'25 pre- Lvlously referred to.. "The other end"of-shaft*32 'exten'dsiinto theinterior of the base housing ahdl as fixed thereon'a crank member, consistinggofj a .disc; 34having acrankpin 35 projecting eccentrically fromits outer: face. 'Shaft 32 andlthe outer arm 12 'are' operatively connected together for corijoint angular movement about their respective pivotalaxesf by means/of a belt cord 26 that extends longitudinally through the interipr of arm 1 and interconnects the pulleys g5 and 3 3. Accordingly; pivotal movement of i w th IQSPBQt to the inner arm is i fim d, by, aturninghiovement of shaft 32 own axis, of equal angular extent. e arm; I l is piyoted' about its axis aft 32' is bodily displaced, or translated about thatiaxis,

gravitational. forc s acting on the inner. and biltenarrns 'of the bracket are transmitted to aft}; tending ito rotate and translate the same a aforesaid. Such forces are opposed by a force from aspring 31,; applied to the crank 35' through a transmission linkage consisting of a'lever rocker element 38 anda link'bar ga spring 31 is preferablyof the helicalycompression variety. Itis, mounted on a guide 'rod '40 that extends axially therethrough. "The spring bears upwardly against an annular shoul der formed by an enlarged integral head portion 4| on the said guide rod, and bears downwardly upon a seat element 42 through which the rod slidably extends. Spring seat 42 is a C-shaped element having aligned apertures in its upper and lower arms 43 and 44 that provide a passage for the lower end portion of guide rod 40.

The upper end of the spring guide rod 40 is positioned by a vertically adjustable abutment, consisting of a screw 45 "threaded in a tab 46 that projects horizontally from the upper margin of a cross plate 41 on the base frame l4. Cross platellis spaced forwardly from the verticalback wall portion 48 of the base frame l4,

Fig The spring adjustment screw has a rounded lower extremity which seats in a spherical socket formed in the guide rod head 4|, the upwardly directed thrust of the spring on the'r'od head causing that part to be retained "against the adjustment screw. The ball andsocke'ttyp'e 'of engagement between the redhead 4| andthe adjustment screw 45 permits the rod'to pi'vot about the'lower end of the screw. The adjustmentscre'w isrend'ered accessible without "rernovin'g' the cover plate I I by an "aligned opening Win the upper endwall of'the baseh'ousin'g. Thus, a screw driver inserted-through the opening '50 may be used toturnj'the adjustment screw and thereby raise or lower the upper spring seat constituted by'th'e rodhead 4|,to effect-a reduction or increase in spring compression. The described spring adjustment means are desirable in order to adjustfor variations in difierent springs, and to obtain 'an'in'itial'balancirig 'of the system. Further spring 'adju'strnehtthei'a 'after'will seldom berequ'ired, unless the-weight load on the bracketarms ischan'g'ed.

Downwardly directed spring force on the spring seat 42*is transm'itted to the rocker element II which ispivoted at olle 'ild'by"a pivot pin-'5! to'a boss 5261'! the base frame. The'ro'ckr elern'ent is p'rovided "with a forwardlypro'jecti'rig bearing pin 53 located approximately midway-betwenits opposite ends. This pin extends into a bearing aperture in the back artiedemmin seat "42, providingapivotal mounting support for the said seat and serving to transmit the spring force therefrom to rocker 38. From'rck'er 3B the-spring 'for'c'eist'rans'mitted to shaftfl by the "linkjbar- 39. This' mei'riber extends" vertically behind the cross plate? and is pivotally 'cdnnctedat its lower end by a-pin 54 to the fre end of rockerSB, and at its upper'end to the shaft crank pin 35.

The crank shaft/"32 is intended-"to remain- 9.1; all'tiin'es in' definite, predetermined angular-relati'oh'shidwith respect to the hub Z l 'Of the outer bracket *armi 2. That relationship 'is'= such that a radius line from thesha'ft axis 'throiigh' the crank pin' 35=a1ways extends" at an angle-013 degrees to the*'ou'ter bracket-arm l2. "This is shown in Fig. 2 wherein it'will 'be observed that the arm 12 is represented" asex't'en'ding horizontally tothe Tightof its pivotal axis,-"and crankpin 35 is located on'a hoiizontal" radius to the left of "the Shaftaxis. The 180' -de'gree relationship aforesaid maintained by 'means which prevent slippage of the belt 'cord fi on either'of the pulleys, consisting-0f cord'clamping tabs "BS-on pulley 36,-anda "screw clar'np assembly 56 on pulley 25 for" anchoring theends of the belt cord.

It will now appear that the outer'arm may be counterbalanced in all positions thereof about its pivotal axis on the inner arm by a force of definite magnitude, acting downwardly on the crank pin 35. Also, the inner arm ll may be counterbalanced in all angular positions thereof about its pivotal axis a; by another force of definite magnitude acting downwardly on the crank pin 35. A single force equal to the sum of those forces, acting on the pin 35 to counterbalance the several bracket arms in their various angular positions, is provided by the spring 37. Because, in the mechanical system herein described, the horizontal distance between the crank pin 35 and the major axis a of the bracket will be a definite and fixed fraction of the horizontal distance between the major axis a and the load object I3, the ratio of the force on the crank pin required to counterbalance the weight of the load object and the arms H and 12 will be approximately the reciprocal of that fraction.

In the improved spring mechanism described and illustrated herein the effective counterbalancing force applied to the crank pin 35 is practically constant, being maintained within very close upper and lower limits for various positions of the bracket arms. Such result is in large part obtained by the described means which reduce to a practical minimum the extent of spring deflection, and which compensate for increased spring force due to deflection, by effecting corresponding changes in the angle at which the spring force is applied to the rocker element 38. Thus, it will be observed, with reference to Fig. '2', that as rocker 38 is caused to swing upwardly about its axis pivot 52, causing increased spring pressure to be applied to the spring seat member 42, the direction of the spring force on the rocker 38 changes, to reduce the effective length of the moment arm on which said increased spring force is acting. Accordingly, the increased spring force is compensated for by the reduction in length of moment arm, and the net result is to produce a substantially constant force on the crank pin 35 to counterbalance the constant gravitational force acting on the bracket. The bracket members may accordingly be easily moved to transfer the supported object from one location to another, as desired, and they will remain in the positions to which they are so adjusted by the counterbalancing action of the described means.

It will be understood that certain changes and modifications may be made in the device herein described without departing from the spirit and full intendment of the invention, which is defined by the appended claims.

I claim:

1. In an adjustable bracket of the character described, a support, a hollow inner bracket arm pivoted at its inner end to the support, an outer bracket arm pivoted to said inner bracket arm, a shaft journalled in the inner bracket arm for rotation about an axis parallel to and spaced from the pivotal axis of said arm, said shaft extending into the inner bracket arm, and means extending longitudinally through said inner arm operatively interconnecting said outer arm and one end of said shaft whereby turning movement of one thereof is imparted to the other, an eccentric bearing member on the opposite end of said shaft and spring counterbalancing means connected to said bearing member.

2. An adjustable bracket of the character described including a base housing, an inner bracket arm having a laterally projecting bearing hub 6. rotatably mounted in the side of the base housing, an outer bracket arm pivoted to the outer end of said inner arm, a shaft extending through said hub portion and journalled therein for rotation about an axis parallel to and spaced from the rotational axis of the said hub, means interconnecting said shaft and the outer bracket arm for conjoint movement about their respective axes, a bearing element projecting eccentrically from said shaft, and spring means connected to said bearing element, adapted to apply a force thereto to counterbalance said inner and outer bracket arms.

3. An adjustable bracket of the character described comprising a base, a hollow inner bracket arm extending from the base at one side thereof, bearing means mounting said bracket arm on said base for pivotal movement in a vertical plane, a transverse shaft carried by said bracket arm at its inner end, said shaft extending eccentrically through said bearing means, an outer bracket arm pivoted to said inner arm, motion transmitting means disposed within the inner arm, said means operatively connecting the .outer bracket arm to said shaft, and spring means in said housing, connected to the shaft to apply a turning force thereto substantially equal and opposite to the turning force thereon produced by gravitational action on said bracket arms.

4. An adjustable bracket comprising a base, a hollow inner bracket arm having a hub portion journalled in said base, an outer arm having a hub portion journalled in the outer end of said inner arm, a shaft journalled in said inner arm hub portion, in spaced, parallel relation tothe axis thereof, linkage means disposed Within said inner arm operatively interconnecting said shaft and the hub of said outer arm for conjoint rotation about their respective axes, and spring means in said base, connected to said shaft, and adapted to apply a force of substantially constant value on said shaft to counterbalance said arms.

5. An adjustable bracket comprising a base, an inner bracket arm having a hub portion journalled in said base, an outer arm having a hub portion journalled in the outer end of said inner arm, a pulley fixed to the hub portion of said outer arm, a shaft journalled in said inner arm hub portion in spaced, parallel relation to the axis thereof, a pulley fixed to said hub portion, a belt linking said pulleys for conjoint rotation, an axially ofiset crank pin on said shaft, and spring means in said base, operatively connected to said crank pin, and adapted to counterbalance said inner and outer arms.

6. An adjustable bracket comprising a base, a jointed bracket arm having pivotally interconnected inner and outer sections, said bracket arm extending forwardly from said base and being pivoted thereto for movement in a vertical plane, a shaft journalled for rotation in the inner end of said inner arm section, said shaft being disposed with its axis parallel to and spaced rearwardly from the pivotal axis of said inner arm section on the base, motion-transmitting means connecting said shaft and said outer arm section for conjoint movement about their respective axes of rotation, and spring means connected to said shaft, said means applying an axially offset force to said shaft tending both to turn and to translate the same downwardly, whereby to effect a counterbalancing of said inner and outer arm sections.

'7. An adjustable bracket comprising a base,

7 a hollow iniier ai'm pivoted to saidibase, mmuter arm'pivoted Eto said innersarxmbothwfisaidi arms being adapted 1170 move :in vertical 'zplanes about their respective pivciise, :a :shait narriedrby and jo'urnaned in 'the inneriendzportioncof $11.25 1111181 arm, seiid shaft being disposed with :its axis :i spaced, parallel relation-11:0 :the -:,\pivota1:.mountin a xis of itheiinner arm, motion: tnansmittingimean within saidinner arm :oprativelyinterconnecb ing :said shaft and :said :outer :arm ;for mom'oinb rotation about their: respective :pivntal gexes, and means :far eequjlibrating said bracket Terms. cluding a. spring and means transmitting :the force '1 of said spring to said. shalft :,1an'd exerting a turning-moment 'of force 1there0n "to 0912030 15 movement f eeaid sh aft :by ;-graviatipnq1 forces acting on saidbracket ,ar-ms.

Q- HE BAL- References Cited in the file pf,th1s patent aUNHEDSTA g ATE S Number -Name "Date 2,200,518 -'Perba1 May 14, 1940 29281-577 Stave, June 23, 1942 10 2,299;251 Perbal Oct. 20, 1942 23547532 Mendelsohn Apr. 3, 1951 FOREIGN PATENTS Number Country Date $551,290 gGreat-Britain -V Feb. 1 6, 1943 

